Chexx CX-83 pcb repair log

hatrick

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I never see any info for repairing these Chexx hockey pcb's, so I figured I'd share my latest repair.

Chexx CX-83 pcb repair log

Status Unkwnown.
First thing I noticed is that the socket at U2 that normally holds a 74ls74 was empty. Placed a 74ls74 in the socket and powered up the pcb hoping for an easy fix. No such luck. No partial playing of the national anthem, nothing, dead board.
The Moog CX-83 pcb has 4 voltage regulators on it, so I figured that was a good place to start. There are two 7805's that provide the +5 for the logic and the Roms, and there is a 78L05 that provides +5 to the audio circuit, and a 78L08 that delivers +8 to the audio circuit.
Everything tested good except for the 7805 at U25. Replacing that returned the missing +5v, but still nothing from the pcb.
While the pcb was on the bench, I tested the electrolytic caps on the board and found that most of them were bad. Replaced all them them for good measure.
Started poking around with the logic probe and noticed the clock signal was missing on the CPU, the custom Moog audio chip and some others I tested. Looks like the crystal was functionaing properly, but the clock signal failed at the 74ls04 at U1. Replaced U1 and now the game booted, but I could not coin up or start a game.
Looking at the schematics, the coin signal goes through the 7417 at U8. Since all ic's on these boards are socketed, it's easy enough to swap parts, so I put in a new 7417, and I was able to coin up and start a game.
I now had a fully functional pcb.
 
They are pretty easy to work on. I think I have a schematic
around somewhere.

Last year I had one with no sound. It was a bad op amp if I remember
correctly.

One of these days I want to dump the ROMs because I'm sure sooner or
later someone is going to need them.

JD

I never see any info for repairing these Chexx hockey pcb's, so I figured I'd share my latest repair.

Chexx CX-83 pcb repair log

Status Unkwnown.
First thing I noticed is that the socket at U2 that normally holds a 74ls74 was empty. Placed a 74ls74 in the socket and powered up the pcb hoping for an easy fix. No such luck. No partial playing of the national anthem, nothing, dead board.
The Moog CX-83 pcb has 4 voltage regulators on it, so I figured that was a good place to start. There are two 7805's that provide the +5 for the logic and the Roms, and there is a 78L05 that provides +5 to the audio circuit, and a 78L08 that delivers +8 to the audio circuit.
Everything tested good except for the 7805 at U25. Replacing that returned the missing +5v, but still nothing from the pcb.
While the pcb was on the bench, I tested the electrolytic caps on the board and found that most of them were bad. Replaced all them them for good measure.
Started poking around with the logic probe and noticed the clock signal was missing on the CPU, the custom Moog audio chip and some others I tested. Looks like the crystal was functionaing properly, but the clock signal failed at the 74ls04 at U1. Replaced U1 and now the game booted, but I could not coin up or start a game.
Looking at the schematics, the coin signal goes through the 7417 at U8. Since all ic's on these boards are socketed, it's easy enough to swap parts, so I put in a new 7417, and I was able to coin up and start a game.
I now had a fully functional pcb.
 
They are pretty easy to work on. I think I have a schematic

around somewhere.



Last year I had one with no sound. It was a bad op amp if I remember

correctly.



One of these days I want to dump the ROMs because I'm sure sooner or

later someone is going to need them.



JD



I was discussing the roms with Steph at hobby roms last week. He has the rom image for the 2716 for both the USA and Canadian national anthem.
He didn't have a dump of the 52164's (which there are 8 of on the pcb). I always assumed those held the national anthem, but maybe they are the notes for the organ tunes, the back ground noise, the boo and cheer?
I'm not sure there is even a replacement for the 52164's. They are 64k with only 24 pins, so do not fit your typical EPROMs size.
 
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